MSDN Documentation

Advanced Topics in ASP.NET Core Web API

This section dives into more complex and advanced features of ASP.NET Core Web API development. Understanding these concepts can help you build more robust, scalable, and maintainable web services.

Dependency Injection in Web APIs

ASP.NET Core has built-in support for Dependency Injection (DI), which is crucial for managing the lifecycle and dependencies of your services. Learn how to register your services and resolve them in controllers and other components.

Key concepts:

• Service lifetimes (Singleton, Scoped, Transient)
• Registering services in Startup.cs (or Program.cs)
• Injecting services into controllers and middleware

public class MyService : IMyService { ... }

public void ConfigureServices(IServiceCollection services)
{
    services.AddScoped<IMyService, MyService>();
    services.AddControllers();
}

public class MyController : ControllerBase
{
    private readonly IMyService _service;

    public MyController(IMyService service)
    {
        _service = service;
    }

    [HttpGet]
    public IActionResult Get()
    {
        return Ok(_service.GetData());
    }
}
            

Asynchronous Programming (async/await)

Leveraging asynchronous programming with async and await is essential for building high-performance, non-blocking Web APIs. This allows your API to handle more concurrent requests efficiently.

Best practices:

• Always return Task or Task<T> for asynchronous operations.
• Avoid blocking on asynchronous calls (e.g., using .Result or .Wait()).
• Use ConfigureAwait(false) where appropriate to improve performance and avoid deadlocks.

public async Task<IActionResult> GetDataAsync()
{
    var data = await _externalService.FetchDataFromApiAsync();
    return Ok(data);
}
            

Web API Performance Optimization

Optimizing your Web API's performance involves several strategies:

• Efficient database queries
• Caching (in-memory, distributed)
• Payload compression (e.g., GZip)
• Minimizing network latency
• Using asynchronous operations effectively

For caching, consider using the Microsoft.Extensions.Caching.Memory package for in-memory caching or Microsoft.Extensions.Caching.Redis for distributed caching.

API Versioning

As your API evolves, you'll need strategies to manage different versions of your API without breaking existing clients. Common approaches include:

• URL Segment Versioning (e.g., /api/v1/products)
• Query String Versioning (e.g., /api/products?api-version=1.0)
• HTTP Header Versioning (e.g., X-API-Version: 1.0)

Libraries like Asp.Versioning (formerly Microsoft.AspNetCore.Mvc.Versioning) can greatly simplify API versioning implementation.

Cross-Origin Resource Sharing (CORS)

CORS is a security mechanism that controls which web domains are allowed to make requests to your API. You'll need to configure CORS policies to allow requests from specific origins.

public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
    // ... other configurations

    app.UseCors(builder => builder
        .AllowAnyOrigin() // Be more specific in production
        .AllowAnyMethod()
        .AllowAnyHeader());

    app.UseRouting();
    app.UseAuthorization();
    app.UseEndpoints(endpoints =>
    {
        endpoints.MapControllers();
    });
}
            

Global Exception Handling

Implement a global exception handler to gracefully manage unhandled exceptions and return appropriate error responses to clients.

Consider using custom middleware or the built-in exception handling middleware.

// Custom Exception Handling Middleware Example
public class ExceptionHandlingMiddleware
{
    private readonly RequestDelegate _next;

    public ExceptionHandlingMiddleware(RequestDelegate next)
    {
        _next = next;
    }

    public async Task InvokeAsync(HttpContext context)
    {
        try
        {
            await _next(context);
        }
        catch (Exception ex)
        {
            // Log the exception
            // Configure the response
            context.Response.StatusCode = StatusCodes.Status500InternalServerError;
            await context.Response.WriteAsync("An unexpected error occurred.");
        }
    }
}

// In Startup.cs/Program.cs:
// app.UseMiddleware<ExceptionHandlingMiddleware>();
            

Swagger/OpenAPI Integration

Documenting your API is crucial for usability. Tools like Swashbuckle integrate Swagger/OpenAPI support into your ASP.NET Core Web API, generating interactive documentation that allows users to test endpoints directly from the browser.